This invention relates to a distributor cap for an ignition distributor for an internal combustion engine.
FIG. 1 is a bottom view of a conventional distributor cap 1 for use with an internal combustion engine of six cylinders, FIG. 2 is a sectional view of the distributor cap 1 taken along line 2--2 of FIG. 1, and FIG. 3 is a side view of an assembly of two electrodes and a conductor assembly connected therebetween.
In FIGS. 1 to 3, the conventional distributor cap 1 comprises a molded cap main body 2, a plurality of external terminals inclucing an input terminal 3 and output terminals 4 disposed on the cap main body 2 so as to be connectable to an external circuit (not shown) such as an ignition coil and spark plugs. The distributor cap 1 also comprises a plurality of inner electrodes including a central electrode 5 and six circumferential electrodes 6 disposed inside of the cap main body 2 for sequential power distribution by a contact rotor of the distributor (not shown). The external terminals 3 and 4 are connected to inner electrodes 5 and 6 by electrical conductor assemblies 8 and 9-14 respectively embedded within the cap main body 2 for electrically connecting said external terminals to said electrodes. The conductor assemblies 8-14 each have an electrical conductor 15 connecting the external terminals 3 and 4 to the inner electrodes 5 and 6. Some of the conductors 15 have formed thereon an electrically insulating sheath member 16, which are cast-molded resin layers on the conductors 15.
Each of the insulating sheath members 16 has integrally formed thereon at least one positioning projection 17 integrally extending from the sheath member 16. The positioning projections 17 disposed on the sheath members 16 are for limiting the movement of the conductors 15 from designed, predetermined positions during the cast-molding of the molded cap main body 2. Therefore, the positioning projections 17 extend substantially perpendicularly to the plane of rotation of the contact rotor. The length of the positioning projections 17 should be sufficiently long during the cast-molding operation of the cap main body 2 so that their tips may engage respective positioning holes formed on the mold and prevent undesirable shifts of the conductors 15. After the cast-molding has been completed, the tips projecting from the mold-formed surface of the cap main body 2 must be cut and removed.
Since the projecting tips of the positioning projections 17 are most preferably cut and removed at the last stage of manufacture of the distributor cap 1, a mechanical stress applied to the positioning projections 17 during the cutting operation sometimes causes separation at the interface between the cast-mold cap main body 2 and the positioning projections 17. Also, since the positioning projections 17 of the conventional distributor cap 1 are arranged so that their central axes intersect with the axes of the respective electrical conductors 15, the positioning projections 17 are located at a position relatively close to the respective electrical conductors 15. Therefore, if the above-mentioned separation at the interface between the positioning projections 17 and the cap main body 2 occurs, a creeping discharge can easily take place at the separated interface, degrading the reliability and the life of the distributor.